1. Field of the Invention
The present invention relates to an electronic image pick-up apparatus which performs photographic operations utilizing a solid-state image pick-up device.
2. Related Art Statement
In general, TTL phase difference type focus detection methods have been used for single-lens reflex cameras capable of photographing utilizing silver salt films. However, it is difficult to match a focal position detected by such a phase differential method with an actual film surface. This is attributable to various factors including errors that occur when a phase difference type sensor module is attached to a camera body and dimensional errors of an optical system that makes up the sensor module.
In general, steps for manufacturing a camera include an operation of adjusting any deviation between a focal position detected using a phase differential method and a film surface. Such an adjusting operation is carried out during a step provided near the final step for manufacturing a camera, and adjustment of the photographic lens is first carried out using an automatic collimator such that an image of an object at a predetermined distance is formed on a film surface. Next, a phase difference type focus detecting operation is performed in this state to determine parameters required for correcting the above-described deviation.
Specifically, rays from an object located equivalently at infinity are projected upon the photographic lens using the automatic collimator, and a sensor is temporarily provided to detect the contrast of an image formed by the photographic lens on the film surface of the camera. The photographic lens is then retracted to the extremity, and the position of the maximum contrast is thereafter detected from the sensor output while protruding the photographic lens to use the amount of protrusion at this time as infinity position information.
In a single-lens reflex camera utilizing a silver salt film, adjustment using an automatic collimator as described above can be easily carried out because the exposed surface of the film is exposed by opening the rear cover.
However, an electronic camera has no rear cover because it is loaded with no film. Therefore, the sensor for detecting contrast can not be temporarily attached.
Further, since an image pick-up device such as a CCD is provided in the position corresponding to the film surface, it is difficult to perform the adjusting operation using an automatic collimator.
It has been therefore necessary to perform an adjustment as described above using a different method in a camera system like an electronic camera in which a surface corresponding to a film surface is not exposed.